Abstract: The morphology structure and photosynthetic characteristics of summer maize (Suyu20 and Zhengdan958) were studied during different growth stages under different water stresses (drought stress, flooding stress and control environment) in potting experiment. The results showed that soil and plant analyzer development (SPAD) value, net photosynthetic rate (NPn), transpiration rate (Tr) and conductance to H2O (Gs) decreased, and the intercellular CO2concentration (Ci) increased under water stresses. The sensitive degrees of two summer maize cultivars to water stresses at tasseling stage were higher than those at jointing stage, and they were further higher to flooding stress than those to drought stress. The drought resistance of Suyu20 was similar to Zhengdan958 at different growth stages, but the flooding resistance of Suyu20 was lower than Zhengdan958. The results provided a theoretical basis for maize water stress research in different regions.

Key words: Summer maize, Drought, Flood, Photosynthetic characteristics, Jointing stage, Tasseling stage